Which two ions are primarily involved in generating an action potential?

• A. Sodium and potassium
• B. Calcium and magnesium
• C. Chlorine and sodium
• D. Potassium and chlorine

Answer: (A)

The generation of an action potential in neurons primarily involves the movement of sodium (Na+) and potassium (K+) ions. When a neuron is at rest, there is a higher concentration of potassium ions inside the cell and a higher concentration of sodium ions outside. During an action potential, a stimulus causes sodium channels to open, allowing sodium ions to rush into the neuron, leading to depolarization of the membrane.

This rapid influx of sodium creates a positive charge inside the cell compared to the outside, which is a critical step in the action potential process. Subsequently, potassium channels open, allowing potassium ions to flow out of the cell. This repolarizes the membrane, restoring the negative charge inside the cell.

Thus, the alternating movements of sodium and potassium ions across the neuronal membrane are essential for the initiation and propagation of action potentials, making them the two key ions involved in this process. The other ion combinations listed do not play a direct role in generating action potentials in the way sodium and potassium do.